Compositions, including esters of citric acid



Patented Sept. 26, 1950 COMPOSITIONS, INCLUDING ESTERS OF CITRIC ACID Hans W. Vahlteich, Edgewater, and Ralph 1!. Neal, North Bergen, N. J., and Chester M. Gooding, Staten Island, N. Y., assignors to The- Best Foods, Inc., New York, N. Y., a corporation of New Jersey No Drawing. Application July 30, 1946, Serial No. 687,236

4 Claims. (or 252-407) Thlsis a continuation-in-part application of theappiications Serial Numbers 608,101, now Pat- No. 2,485,631, and 608,102, now Pat. 2,485,632, filed July 31, 1945, and the application Serial Number 608,380, now Pat. 2,485,633, filed August 1. 1945.

This invention relates to citric acid ester compositions, and more particularly to compositions including esters of citric acid.

An object of this invention is to disperse relatively readily and uniformly esters of citric acid, and particularly monoesters or diesters of citric acid throughout a mass of oil.

Another object of this invention is to provide compositions which retard the development of rancidity and ofi-fiavor in glyceridic oils and which may be quickly disseminated throughout a mass of glyceridic oil.

Another object of this invention is to incorporate in glyceridic oils monoesters or diesters of citric acid which due to their limited solubility or relative immiscibility per se in glyceridic oils, are difiicult to incorporate therein.

Monoesters of citric acid have been found to retard for relatively prolonged periods rancidity in glyceridic oils, while mixtures of mono, di and triesters of citric acid are effective as emulsifiers. Some of these esters of citric acid, however, particularly the lower mono and di-alkyl esters of citric acid, due to their limited solubility or relative immiscibility in the oil, are not readily dispersed uniformly throughout a mass of oil. And to retard efiectively the development of rancidity and olT-fiavor of these oils, it is essential that the esters of citric acid be dispersed relatively uniformly throughout the mass of the oil.

In accordance with this invention, compositions comprising esters of citric acid are provided which may be readily dispersed throughout a mass of oil. These compositions comprise a solubilizing agent and an ester of citric acid, such as a mono or di-alkyl ester of citric acid or a mono or dialkylene ester of citric acid. These compositions may contain a plurality of citric acid esters, such as a mixture of mono, di and triesters of citric acid which may be derived from the same or a plurality of different alcohols and citric acid. The solubilizing agent maybe, for example, a monocarboxylic acid having at least carbon atoms; a monocarboxylic acid monoesterof glycerol or propylene glycol or their polymers, the monocarboxylic acid having at least 10 carbon atoms; a phosphatide such as lecithin; an oil-soluble aliphatic alcohol having at least 6 carbon atoms, esters of polyhydric alcohols or 2 their polymers; or others and anhydrides of polyhydricalcohols.

The compositions of this invention may be readily dispersed uniformly throughout a mass of oil, such as glyceridic oil. Some ofthe esters of citric acid are soluble only to a limited degree in glyceridic oils or mixtures containing glyceridic oils. This is particularly true of the monoalkyl esters of citric acid in which the alkyl group has less than 6 carbon atoms or mono or dialkyl esters of citric acid or mixtures of mono, di and triesters of citric acid which are relatively high melting solids. While the glycericlic oil may be heated to dissolve some of these esters of citric acid, such heating, particularly if a high temperature is required, materially damages the oil for some purposes.

The compositions of this invention are prepared by dissolving the ester of citric acid. or mixtures of ester in the solubilizing agent. The resulting compositions may then be addedto a mass of an oil. such as a glyceridic oil. The resulting mixture may, if desired, be agitated at a suitable temperature, such as 40 to 60 C. The agitation readily disperses the composition" uniformly throughout the mass of the oil and, as a consequence, a relatively homogeneous product is obtained.

The solubilizing agent must be capable of dis-.

solving a material quantity of the ester or plurality of esters of citric acid at the temperatures at which the compositions are to be used. The

solubilizing agent must also be miscible with the glyceridic oil or other oil to which the compositions of this invention are to be added. Moreover, from a practical standpoint the, ultimate concentration of the soli1biiizingagentmust not unduly contaminate the oil to which these compositions are added. For example, a large'volume of a monocarboxylic acid, such as stearic acid, desirably should not be employed if the compositions are added to a glyceridic oil since it would materially increase the free fatty acid content thereof which would render the oil unsatisfactory for many purposes. However, the amount of the esters'of citric acid required to impart the desired characteristics tolan oil for most purposes may be addedas a composition of this invention comprising the required ester of citric acid and the solubilizing agent without unduly increasing the free fatty acid content of the When the compositions of this invention are added to a glyceridic oil, even though the esters of citric acid, and particularly the mono and diesters of citric acid, are only slightly soluble therein, the esters are thrown out of the solubilizing agent in a finely divided state to form a liquesol and thereby present a very large surface in contact with the glyceridic oil. As a result, they are easily dispersed throughout the main body of the treated oil, and eventually dissolve especially when the main body of the oil is kept agitated.

Examples of the monocarboxylic acid monoesters of glycerol or propylene glycol or their polymers which may be employed as solubilizing agents are the monostearyl glycerides. monooleyl glycerides, monolauryl glycerides and monopalmityl glycerides, or their corresponding polyglycerol esters or mixtures thereof. These monocarboxylic acid monoesters, as commercially prepared, contain substantial amounts of the corresponding monocarboxylic acid diesters and small amounts of the corresponding monocarboxylic acid triesters. Such monocarboxylic acid monoesters as commercially prepared may be employed as the solubilizing agents in the compositions of this invention. Monoglycerides prepared from an edible oil, such as cotton seed oil, have been found to be very satisfactory solubillzing agents.

Examples of saturated monohydric alcohols which may be employed as solubilizing agents are Z-ethylhexyl alcohol, n-octyl alcohol, stearyl alcohol, cetyl alcohol and myristyl alcohol.

Examples of the fatty acids which may be employed as solubilizing agents are stearic acid, palmitic acid, oleic acid, lauric acid and myristic acid.

Examples of the esters which may be employed in the compositions of this invention are the mono, di or triesters of citric acid derived from the following alcohols: n-propyl, isopropyl, n-butyl, crotyl, isobutyl, isoamyl, 2-ethylhexyl, lauryl, myristyl, palmityl, oleyl and -stearyl.

Mixtures of monoaliphatic esters of citric acid, mixtures of dialiphatic esters of citric acid, mixtures of trialiphatic esters of citric acid, or mixtures of mono, di and trialiphatic esters of citric acid may be employed in the compositions of this invention. For example, a mixture of different monoalkyl esters of citric acid may be dissolved in the solubilizing agent. Or again, different monoalkylene esters of citric acid may be dissolved in the solubilizing agent; or a mixture of a monoalkyl ester and a monoalkylene ester may be employed.

Mixtures of various solubilizing agents may be utilized to effect uniform dispersion of the aliphatic esters of citric acid throughout the glyceridic oil. For example, a mixture of lauryl alcohol and cetyl alcohol may be employed to effect the solubilizing of monoisopropyl citrate in the glyceridic oil. Altcrnately, a mixture of different monocarboxylic acid monoesters of glycerol or propylene glycol may be utilized for the solubilizing of the esters.

The esters used in the compositions of this invention are prepared by the esterification of citric acid and a monohydric alcohol preferably in proportions which favor the formation of the mono, di or triesters whichever is predominantly desired. The esterification may be conducted by any of the Well known methods employed for the production of esters, and the resulting reaction mixture which comprises the mono, di and triesters of citric acid is subjected to treatment with solvents which dissolve the monoesters but do not dissolve any appreciable amounts of the di and triesters, or alternately solvents which dissolve the di and triesters but do not dissolle appreciable quantities of the monoesters. By repeating the treatment with these solvents, a relatively pure monoester of citric acid may be obtained. The di and triesters may be obtained in pure form, if desired, by following a similar procedure to that used in the production of the monoester by utilizing appropriate solvents. If desired, for some uses the esters need not be sen-- arated, but the entire reaction product including mono, di and triesters of citric acid may be dissolved in the solubilizing agent to form the composition of this invention.

A more comprehensive understanding of this invention is obtained by reference to the following examples:

Exampl 1.Composition containing monoisoowl citrate and monocarboxylic acid monoesters of glycerol One gram of monoisopropyl citrateis dissolved in 5 grams of monocarboxylic acid monoostcrs of glycerol prepared from a winterized, refined unhydrogenated but deodorized corn oil. The monocarboxylic acid monoesters of glycerol are prepared from this corn oil by reacting glycerol with the corn oil in the presence of sodium bicarbonate. The amount of oil and glycerine added are such as to produce predominantly the monoacyl derivatives of-the fatty acid components of the corn oil.

The solution of the monoisopropyl citrate in the oil-coupling agent may be utilized to distribute the monoisopropyl citrate uniformly throughout a body of vegetable oil. For example. the solution may be added at a temperature of about 35 to 50 C. to 10 kilograms of a winterized refined, unhydrogenated, but deodorized corn oil suitable for use as a cooking and salad oil. The corn oil prior to the addition of the solution of the monoisopropyl citrate is heated to a temperature of 35 to 50 C. The mixture is then agitated to disperse uniformly the monoisopropyl citrate throughout the oil.

The monoisopropyl citrate is prepared as follows:

Equal parts of U. S. P. citric acid and commercial 99% isopropyl alcohol are heated together under reflux, without catalyst for 118 hours at 92 C., after which time the acid value of the reaction mixture is found to be about 203.6 and the saponification value 392 (about one-half esterified). reaction are removed by low temperature evaporation in vacuo.

The residue is taken up with ethyl ether and then thrown out of the ether solution by the addition of a quantity of low-boiling petroleum ether just suflicient to form a precipitate. The precipitate or oily residue is again taken u with ethyl ether and the precipitation with low boiling petroleum ether repeated. This procedure is repeated several times. solvent by heating with stirring to 130 C. a typical analysis is:

This product solidifies after long standing and and consists of a mixture of about monoester and 10% diester. The resulting product,

The alcohol and most of the water of After final removal of pared as described herein is obtained by dissolvwithout further purification, may be used to Exampl 4.Composition containin mono, di form the solution with an oil-solubilizing agent.. and triethyl citrates and monocarbozylic acid such as the monocarboxylic monoesters of glycermonoesters of glycerol me harem described Mono, di and triethyl citrate are dispersed mu- 5 formly throughout lard by a, composition com- Example 2.Composition containin mono, di prising monoethy] t t m t t t mand tri s m ml ciirates d mo c r r ethyl citrate and monoglyceroi mohoesters of the acid monoesters ofalil erol fatty acid componentsof the lard to which it is The composition of this example may be uti- 233 51 5 fif z gz citrate methyl citrate prepared simultaneously for dispersing monoisopmpyl citrate. by the method hereinafter described, and the throughout a mass of a glyceridic oil, such as mixture of mono, di and methyl citrates is dis? corn salad 01]. The composition comprises monosolved in the monoglycerol monoesters prepared 1sprpy1 citrate meme with the diisopropyl from fatty acid components of the lard. 50 grams citrate and triisopropyl citrate and the monoglyc- 10 of the mixture of mono, di and methyl eihetee erol ester of the fatty acid components of suba added to 50 grams of the memelyeeml mene stantially any vegetable oil, but conveniently the ester The meneglyeerel mehee'eters are monoglycerides of the fatty acid components of pared in the same manner as the meneglyeeml the corn salad Oil t0 which this mixture 18 to be monoesters in Example 1 The amount of mono. added. The monoisopropyl ci pr p ethyl citrate in the mixture of. mono, di and tricltr e and i P PyI citrate and the monoglycethyl citrates is about 75%. 1 cc. of the solution erol esters are preferably mixed with a quantity of the mixture of ethyl citrates in the monoglycof the 011 being treated to form homogeneous erides is added to 1 kilogram of lard maintained mixture. The mixture of esters is produced as at a temp rature of about 50 C. and agitated to follows: eflect dispersion of the composition throughout 260 grams of anhydrous citric acid are mixed the with 130 grams of commercial 99% isopropyl al- The mixture of P citratedlethyl cohoi, and the mixture is heated at 155 C. for 2 rate and triet'hyl hate is Prepared as follow-5: hours in a closed vessel. The pressure developed 96 s of anhydrous citric acid and 300 of by alcohol eel-responds to about 55 per absolute ethanol are refluxed for 3 days. The exsquere The alcohol is then evaporated cess ethanol is removed by evaporation ona steam der reduced pressure with a nitrogen stream at bath Typical acid and saponmcaflon values of 130 C. A typical acid value of the resulting the resulting mixture are: product is 386 and a typical saponification value 35 Acid value 258.2 702. A typical ratio of free carboxyl to total car- I Saponification value 680.7

boxyl is 0.55.

38 parts of these mixed isopropyl esters of cit- Example containing ric acid are dissolved in 44.3 parts of monoglycerand misomom'l citmtes and oleic acid ides prepared as described in Example 1 together 40 One part of the mixed mono, di and triisopropyl with 17.7 parts of the corn salad oil to be treated. citrates prepared in accordance with Example 2 Preferably the 17.7 parts of the oil to be treated are dissolved at a temperature'of about 140 F.-in are added to the crude monoglycerides after their 5 parts of oleic acid. The resulting compomtion preparation and before washing. This procedure is clear at that temperature and may be utilized aids in separation of the wash water and defor dispersing the mono, di and triesters throughcreases the degree of spontaneous esteriflcation out a body of a glyceridic oil. The'soiution of the of the free carboxyl groups of the isopropyl citmixed esters dissolved in the oleic acid was homorates by the free hydroxyl groups of the monoseneous at above 58? C. low this P l iglycerides. The washing with water, moreover, ness appeared which eventually would result in a removes excess glycerol. two-layer separation. Desirably, therefore. the

A solution of the mixed isopropyl ester prea solution is added 130 the glyceridic 011 above 58 C.

Ezample 6..Composition containing relatively in 38 am of the mixed esters in 62 rams of g gr 8 pure diisopropyl citrate and stearic acid monoglycerol esters of the fatty acid components of corn oil. Relativelypure-'diisopropyl'citrate wasobtained 10 cc. of this'solution are added to 10 kilofrom the mixed isopropyl esters obtaliie'dinad grams of corn salad oil. The oil prior to the addi-- -d e with the'm thod d s ribed in Example tion is heated to a temperature of about 50 0.. 2, b 'th use of suit bl solv nt su h a ethyl and during the addition. the mixture is agitatedether and petroleum ether. 40 parts of the result- 7 By this procedure, the mixed esters are dispersed to lug substantially pure diisopropyl citrate was disuniformly h oughout the mass of the corn oil. solved at about 140 F. in parts of stearic acid. This composition was homogeneous almost down Example 3.--Composition containing mono, (ii to the solidification point of the mixture. If it is and triisopromll citrates and oleyl alcohol to be utilized to disperse uniformly the diisopropyl 6.5 citrate throughout a mass ofglyceridic oil suchas 5 parts of mixed isopropyl citrate prepared in corn oil, .the composition shouldbeadded at. a' accordance with the procedure outlined in Exam-.- temperature above t melting point of te -1 pie 2 are dissolved in 20 parts of oleyl alcohol. a id,

25 cc. of this solution are added to 5 kilos of unhydrogenated and undeodorized sunflower seed Example containing mm,

oil. During the addition of the solution of the and citrate? and relatively 9"" mixed isopropyl citrates, the mixture is agitated m glycol steamte vis r uslyhe m d p py t a s ar s- 10 partsof the mixed isopropyl eitrates obtained persed throughout the mass of the sunflower seed in accordance with the method described in Ex- 1 76 ample 2 are dissolved at a temperature of about 7 140 F. in 50 parts of relatively pure propylene glycol stearate.

Example 8.Compositin containing mono. di and triisopropyl citrates and lecithin 78 parts of the mixed isopropyl citrates prepared in accordance with Example 2 are dissolved at a temperature of about 140 F. in 124 parts of lecithin.

Example 9.-Composition containing 2-ethylhexyl acid citrate and sorbitol distearate parts of 2-ethylhexyl acid citrate are dissolved at a temperature of about 140 F. in 10 parts of sorbitol distearate. The 2-ethylhexyl acid citrate is prepared in a manner similar to that described for the preparation of the isopropyl citrates in Example 2, by reacting citric acid with 2-ethylhexyl alcohol.

Example 10.-Composition containing lauryl acid citrate and diglycol laarate Example 11.C0mpositi0n containing relatively pure monostearyl citrate and trioleyl citrate 10 parts of relatively pure monostearyl citrate were dissolved at a temperature of 140 F, in parts of trioleyl citrate. The relatively pure monostearyl citrate was prepared as follows:

12.1 kilograms of citric acid monohydrate are added to 30 kilograms of commercial stearyl a1- cohol which is previously melted. During the addition, the mixture is agitated. The mixture is held at 150 C. under reduced pressure for a period of 1 hours. At the end,of this period, boiling and foaming cease substantially. The resulting product which consists of a mixture of monostearyl citrate, distearyl citrate and tristearyl citrate has an acid value of about 83, a saponiflcation value of about 249.0 and a melting point of about 51-68 C. and a color on the Lovibond scale of about 36Y5.8R. (5% inch column).

The trioleyl citrate was prepared by reacting citric acid and oleyl alcohol in such proportions as to favor the formation of the trioleyl citrate. The composition containing the relatively pure monostearyl citrate and trioleyl citrate was clear and homogeneous when warm and suitable for adding to an oil.

The terms and expressions which we have employed are used as terms of description and not of limitation, and we have no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invention claimed. 1

What is claimed is:

1. A composition of matter consisting essentially of an edible, oil-miscible vehicle having dissolved therein a monoester of citric acid selected from the class consisting of monoethyl citrate, monolsopropyl citrate, mono-n-propyl citrate, monocrotyl citrate, mono-n-butyl citrate, monoisobutyl citrate, monoisoamyl citrate, mono-2- ethylhexyl citrate, monolauryl citrate, monomyristyl citrate, monopalmityl citrate, monooleyl citrate and monostearyl citrate, the amount of said monoester being 15 to 37 /2% of said composition.

2. A composition of matter in accordance with claim 1. in which the edible, oil-miscible vehicle is monoglycerides of a fatty acid in which the fatty acid group has at least 10 carbon atoms.

3. A composition of matter in accordance with claim 1, in which the edible, oil-miscible vehicle is a monohydric aliphatic alcohol having at least 6 carbon atoms.

4. A composition of matter in accordance with claim 1, in which the edible, oil-miscible vehicle is a fatty acid having at least 10 carbon atoms.

HANS W. VAHLTEICI-I. RALPH H. NEAL. CHESTER M. GOODING.

REFERENCES CITED The following references are of record in the file of. this patent:

UNITED STATES PATENTS Number Name Date 1,805,458 Rogers May 12, 1931 1,857,274 Emhardt May 10, 1932 1,898,363 Greenbank Feb. 21, 1933 2,122,716 Graves July 5, 1938 

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF AN EDIBLE, OIL-MISCIBLE VEHICLE HAVING DISSOLVED THEREIN A MONOESTER OF CITRIC ACID SELECTED FROM THE CLASS CONSISTING OF MONOETHYL CITRATE, MONOISOPROPYL CITRATE, MONO-N-PROPYL CITRATE, MONOCROTYL CITRATE, MONO-N-BUTYL CITRATE, MONOISOBUTYL CITRATE, MONOISOAMYL CITRATE, MONO-2ETHYLHEXYL CITRATE, MONOLAURYL CITRATE, MONOMYRISTYL CITRATE, MONOPALMITYL CITRATE, MONOOLEYL CITRATE AND MONOSTEARYL CITRATE, THE AMOUNT OF SAID MONOESTER BEING 15 TO 37 1/2% OF SAID COMPOSITION. 